Early changes in Huntington's disease patient brains involve alterations in cytoskeletal and synaptic elements

Area of Science:

• Neuroscience
• Cell Biology
• Pathology

Background:

• Huntington's disease (HD) results from polyglutamine expansion in huntingtin protein, with pathogenesis potentially involving toxic gain-of-function.
• Aberrant protein interactions are suspected in HD, but early cellular changes remain unclear.

Purpose of the Study:

• To investigate early degenerative changes in cytoskeletal and vesicular components in the frontal cortex of Huntington's disease patients.
• To identify alterations in neuronal fiber density, cytoskeletal markers, and synaptic proteins during presymptomatic and early pathological stages of HD.

Main Methods:

• Morphologic analysis using silver impregnation.
• Immunocytochemistry for cytoskeletal markers (alpha-tubulin, MAP2, phosphorylated neurofilament) and synaptic proteins (dynamin, PACSIN 1).
• Immunoblotting for synaptic proteins (complexin 2).

Main Results:

• Progressive decrease in neuronal fiber density and organization observed starting in presymptomatic HD cases.
• Loss of staining for cytoskeletal markers and reduction in complexin 2 levels in early and late-stage HD.
• Striking loss of dynamin and PACSIN 1 by immunocytochemistry, suggesting abnormal distribution, despite unchanged immunoblotting levels.

Conclusions:

• Mutant huntingtin impacts synaptic function and cytoskeletal integrity before clinical symptoms manifest.
• These early cellular changes may influence the onset and progression of Huntington's disease.